1. Field of the Invention
The present invention generally relates to a catheter as well as a method for producing same.
2. Background Information
For an expansion of a stenosis in body vessels or body hollows, catheter arrangements are used nowadays which comprise an expandable balloon at their distal ends. A stent may additionally be crimped on the expandable balloon, which can be placed in the stenosis for stabilizing the vascular wall. The catheter arrangement is guided to the constricted position in the patient's body with the help of a guiding wire. The stenosis is then expanded by expanding the balloon or the crimped stent is placed in the stenosis, respectively.
A catheter having a soft tip is disclosed in U.S. Pat. No. 4,782,834. However, the soft tip of this catheter is achieved by a material transition to a material of lesser stability. This means that the complete tip is made of the soft material, resulting in the problem that this portion tends to bend. A possible result thereof is a deformation of the tip, which may lead to a constriction of the inner lumen or a permanent deformation.
The quality of a balloon catheter stands out due to the fact that the catheter can follow winding vessels easily and that the catheter can be pushed as far as possible into a stenosis, guided by the guide wire (“tracking”). This tracking is supported by the fact that the tip is flexible enough to guide the balloon. In case when in particular the distal end, also referred to as tip, is made from an especially suitable flexible material, the complete system follows the windings of the vessel. At the same time, it has to be guaranteed that the catheter can be securely pushed into the constricted portions of the vessel. This property is referred to as “pushability”. In case the complete catheter tip, as that of the U.S. Pat. No. 4,782,834, is formed of a soft material, in particular this required property is negatively affected. When pushing the catheter tip, same can be deformed reversibly or irreversibly and therefore also an entangling at the guide wire can occur (friction). With decreasing size of the profile of the tip, i.e., the smaller the so-called leasion entry profile, the more the mechanical sensitiveness of the tip increases and the more are the properties of the tip negatively affected by the soft material.
However, as it is desired to have an entry profile of the catheter as small as possible in order to penetrate narrow stenoses, it would be ideal to be able to form a tip having a minimum entry profile but being mechanically stable, featuring a continuously increasing diameter, but being flexible and having a homogenous transition into the balloon cone.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved catheter. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.